Method of joining oil well casing and tubing with adhesive



March 24, 1970 3,502,150

METHOD OF JOINING OIL WELL CASING AND TUBING WITH ADHESIVE H. F. DUNLAP Filed May 7. 1968 Jill INVENTOR Henry F. Dunlap J-W Attorney I I United States Patent METHOD OF JOINING OIL WELL CASING AND TUBING WITH ADHESIVE Henry F. Dunlap, Dallas, Tex., assignor to Atlantic Richfield Company, Philadelphia, Pa., a corporation of Pennsylvania Filed May 7, 1968, Ser. No. 727,218

Int. Cl. EZlb 17/08 US. Cl. 166-315 8 Claims ABSTRACT OF THE DISCLOSURE Two sections of casing or tubing made of steel, or glass, or one of steel and one of glass, being placed in well bore are joined with a very fast setting nonmetallic organic adhesive in a way that the adhesive sustains the tensile forces created when running the casing or tubing. The adhesive bonding system has sufficient tensile shear strength and area to withstand these tensile forces. The adhesive will either thermally decompose or become sufiiciently plastic so that upon the application of the proper amount of energy the joints may be broken and cleaned whenever required. This method of joining casing or tubing replaces threaded and welded joints and is especially useful for joining glass casing or tubing.

BACKGROUND OF THE INVENTION This invention relates to a new way of placing sections of steel or glass casing or tubing in a borehole for producing oil and gas wells and to a new use for adhesive joints.

In the oil industry, casing and tubing are placed in a subsurface borehole or well so that fluid may be produced from or injected into a subsurface formation. Casing is tubular pipe which is usually cemented in place by forcing cement into the annulus between the casing and borehole. The usual size is between four and one-half inches and thirteen and three-eighths inches. There are generally three main casings run in a well. These are called the surface string, the protective (or intermediate) string, and the production string. The surface casing seals and isolates fresh water sands near the surface. Then length of the surface string ranges from five hundred feet to four thousand feet. The protective string of casing is used for such purposes as to cover and seal salt stringers, to cover and protect weak formations and the like. The length of the protective string usually ranges from two to fifteen thousand feet. The production string of casing is set to isolate and enable production of the producing zone. The casing and the joints connecting the sections of easing are designed to resist collapse pressure and to resist internal pressures. These design pressures will be at least as great as the pressure exerted by an appropriate column of water. The casing and joints are also designed to have sufficient resistance to tensile shear or tensile forces to support the weight of the casing below the joint and section under consideration. If necessary, this tensile design requirement could be relaxed somewhat by taking advantage of buoyancy by floating the casing into a mud filled well bore. After the casing is run into the borehole, cement is pumped into the annulus around the outside of the casing for some or all of the length of the casing. While the casing is being cemented, it is desirable to reciprocate the casing in the hole over about thirty feet to insure good placement of the cement. The casing must be strong enough to permit this.

The tubing is smaller than the casing and is run through the inner string of casing. The tubing is designed to 3,502,159 Patented Mar. 24, 1970 resist the same collapse and formation pressures as is the casing; however, since the tubing may hang unsupported inside the casing or may be called upon to support, release and set packers, the tubing is usually designed to support more than its own weight.

Reference may be had to various statistical publications for the quantities and sizes of casing and tubing used each year in oil and gas production; moreover, reference may be had toother publications for a more detailed discussion of the principles of designing casing and tubing strings.

The length of the sections of both tubing and casing is presently standardized at thirty feet. When a string of casing or tubing is run in or out of the borehole, sections are usually added or removed singly or two at a time while the sections in the borehole are suspended between dogs or slips. In the case of steel pipe, these dogs or slips bite into the outer wall of the casing or tubing. In the case of glass pipe, lugs, couplings or other frictional means hold the glass pipe without damaging the surface of the glass.

Sections of easing or tubing are joined by threaded connectors which must withstand the same pressures as the pipe itself. These connections are made up tight by chaining or power tongs which mar the outside of steel pipe. If the pipe were glass, it would be necessary to provide wrench lugs or flats which would be used to make up the threaded connections. It has been proposed to use various plastics and other coupling compounds to enhance the sealing properties of threaded steel casing or tubing couplings, but it has not been proposed to use an adhesive joint to hold glass and steel casing or tubing together in such a way that the adhesive sustains the entire tensile load.

The threaded ends of the pipe must be strong enough to withstand the design factors previously mentioned. Rather than overdesign the bulk of the pipe between the threaded ends, it is usual practice to add extra wall thickness at the threaded ends so that the ends will have the same strength as the remainder of the section.

Another way to connect sections of casing or tubing is to use fusion metallic welding. Welding has the disadvantages of being diflicult to apply, hazardous, permanent, creating stress and galvanic corrosion and cracking, and other related disadvantages.

This invention provides a new way of coupling the casing and tubing of oil and gas wells which method involves a new usefor strong nonmetallic adhesives.

' SUMMARY OF THE INVENTION This invention provides a new use for strong nonmetallic adhesive joints and a new way of placing hollow tubular sections of casing or tubing in a well to form at least fifty percent of a well string. The sections are composed of material selected from the group consisting of steel or glass. The sections are placed in the well bore by connecting first and second sections with an organic adhesive in a manner such that the adhesive sustains the tensile forces created by the weight of sections below the adhesive connection. The adhesively connected sections are then lowered into the well with the first section being suspended by the adhesive connection from the lower end of the second section. Another section is then connected to the upper end of the second section and the process is repeated until the adhesively connected sections form at least fifty percent of the well string. Preferably, the adhesive will be an epoxy base adhesive which sets within three minutes to a tensile shear strength suflicient to suspend the sections below the adhesive as the sections are lowered into the well bore. The step of adhesively connecting the two sections will include suspending the first section with its lower end in the well and its upper end above the surface. The second section is then suspended above and in alignment with the suspended first section and with the lower end of the suspended second section above the upper end of the first section. The adhesive is then applied to a surface on either the upper end of the first section, or on the lower end of the second section, or on both ends. Very quickly thereafter, the suspended second section is lowered into contact with either the end of the first section or a coupling. This compresses the adhesive and, while the adhesive is thus in compression, it is heated to rapidly set the adhesive. There may be a coupling made of either glass or steel on either the upper end of the first section or on the lower end of the second section to provide greater contact area and other advantages. If the coupling is on the lower end of the second section, the adhesive will usually be applied to the exterior end side surface of the upper end of the first section and the coupling lowered onto this adhesively coated end. This pushes excess adhesive downward and compresses remaining adhesive between the interior surface of the coupling and the exterior end surface of the upper end of the first section. In contrast, if the coupling is on the upper end of the first section, the adhesive will usually be applied to the exterior end surface of the lower end of the second section and this lower end will be lowered into the coupling.

BRIEF DESCRIPTION OF THE DRAWINGS The drawing is a vertical, broken, cross-sectional view illustrating ways of joining sections of glass or steel casing or tubing by placing the sections in a well bore.

DESCRIPTION OF PREFERRED EMBODIMENTS Briefly, this invention provides a new use for strong, rapid setting, nonmetallic adhesives and a new way of placing or running steel or glass casing or tubing in a well wherein the hollow tubular sections of easing or tubing are joined by an adhesive in such a way that the adhesive sustains or bears the tensile load or forces created by the weight of the sections below the adhesive connection.

More specifically, as illustrated in the drawing, hollow tubular sections are placed in well 11 to form at least fifty percent of well string 13. The hollow tubular sections are composed of a material selected from the group consisting of steel or glass. As used herein, glass is that type of glass formed upon the controlled cooling of a molten silica base material or the extremely strong type of glass which is composed of ceramic crystals in a noncrystalline silica base matrix.

Several types of joints for the tubular sections are shown. In joint 15, the lower end of tubular section 17 has a beveled end surface and the upper end of tubular section 19 has an oppositely beveled end surface. The two beveled end surfaces are arranged so that the surfaces will mate.

In joint 21, the upper end of tubular section 17 has a coupling with slightly tapered interior surface 23. The lower end of tubular section 25 has a male end with slightly tapered exterior surface 27. The coupling and male end are arranged so that interior surface 23 and exterior surface 27 will mate when the lower end of section 23 is placed in the coupling.

Joint 29 is similar to joint 21 except for the fact that in joint 29 the coupling is on the lower end of tubular section 31 and is above the upper male end of tubular section 25.

In joints 21 and 29, the couplings are shown as integral parts of the tubular sections. As illustrated in joint 33, it is not necessary that the coupling be an integral part of a tubular section. In joint 33, coupling 35 is on the upper end of tubular section 31 which has a slightly tapered outer surface. Coupling 35 has a slightly tapered interior surface which mates with the outer surface of the upper end of tubular section 31. Coupling 35 may be made of either glass or steel.

As shown, tubular section 31 is suspended by a removable suspending clamp or hanger which is simply represented by block 37. Means for suspending casing and tubing are well known and are not described herein. Tubular section 31 is thus suspended with its lower end in well 11 and its upper end above the surface. Tubular section 25 is suspended from the lower end of tubular section 31 with joint 29 sustaining the tensile load of suspending tubular section 25. In like manner tubular section 17 is suspended from the lower end of tubular section 25 by joint 21 and tubular section 19 is suspended from the lower end of tubular section 17 by joint 15.

Above and in alignment with the upper end of tubular section 31 and coupling 35, there is suspended tubular section 39 whose lower end is ready to be lowered into coupling 35. The means for suspending tubular section 39 are not shown since such means are well-known in the earth drilling art.

In all of the joints just described, the tensile forces created by the weight of the tubular sections below a given joint are borne by an organic, nonmetallic adhesive which joins the tubular sections. In other words, there are no threads or similar mechanical suspending members which sustain any portion of these tensile forces. The adhesive bonding system has sufficient tensile shear strength to support this tensile load. The amount of tensile load that a well-formed adhesive joint may withstand is estimated by multiplying the tensile shear strength of the adhesive in pounds per square inch by the area of the adhesive joint in square inches. The tensile load applied to the adhesive joint may be approximated by the weight of the tubular sections below a given joint. The actual tensile load will also depend on the use to which the casing or tubing is subjected. If desired, in some instances the tensile load may be reduced by fioating the adhesively connected casing or tubing into a well filled with a dense mud. The tensile load below a joint will, therefore, depend on the density, size and length of the casing or tubing sections below the joint. As mentioned previously, the overall length and the size of the casing strings will vary depending on the reasons for installing each casing string. By the same token, the length of the tubing string will vary with the depth of the formation. As an example of how the necesasry strength of the adhesive may be determined, consider a 5 /2 inch O.D., J-55, 17 pound per foot steel casing string 4000 feet long connected with a coupling equivalent in area to the standard short coupling. The area of the joint for the short coupling is 60.5 square inches. The weight of the steel casing below the top joint would be approximately 68,000 pounds. The tensile shear strength required for the adhesive would be 68,000 pounds divided by 60.5 square inches and multiplied by an appropriate safety factor. The required tensile shear strength of the adhesive would be at least 1124 pounds per square inch times the appropriate safety factor. If only the lower fifty percent of the casing string were joined with adhesive, the uppermost adhesive joint would be near the middle of the string and the necessary tensile shear strength would be only half this valve. By the same token, if the entire casing string were made of glass having a density one-third that of steel, the necessary tensile shear strength for the top joint would be one-third of this value.

As mentioned previously, the casing and tubing used herein is made either of glass or steel. The couplings, if any, are also made of either glass or steel. In other words, the sections joined with the adhesive involve only steel-tosteel joining, or glass-to-glass joining, or glass-to-steel joining. Some adhesives suitable for one or more of these types of joints are the epoxy, phenolic, and urethane base adhesives. For example, epoxy, nylon-epoxy, epoxyphenolic, nitrile-phenolic, vinyl-phenolic, and elastomerphenolic are suitable for joining metal-to-metal or metalto-glass, or glass-to-glass. By way of further example, an alkyl 2-cyan0acrylate adhesive was used to join glass-toglass in less than a minute and steel-to-steel in less than three minutes and the resulting tensile shear strength of the adhesive was greater than 3400 pounds per square inch.

Since the adhesive joint is used primarily in place of the usual threaded couplings for casing and tubing, it is simpler to select an adhesive joining system that provides a joint as strong as a threaded coupling. The threaded short coupling for the J-55 casing in the example just given has a coupling strength of 234,000 pounds and an area of 60.5 square inches. An adhesive joint of the same area would need a tensile shear strength of 234,000 pounds divided by 60.5 square inches or 3870 pounds per square inch. Epoxy adhesives, which are preferred for this use for reasons hereinafter set forth, have tensile shear strengths well in excess of 3870 pounds per square inch.

In addition to providing adequate strength, the adhesive selected should exhibit low shrinkage and low coeflicient of expansion, a high degree of adhesion to steel and glass, high impact strength and shock absorbence, chemical resistance to brines and aliphatic hydrocarbons, thermal stability to 400 F., and high fatigue endurance. It is, moreover, necessary that the adhesive set rapidly to the high tensile shear strength required. It is much preferred if the adhesive will thermally set to the required tensile shear strength within three minutes or less.

It will be necessary to break the joints when pulling tubing or casing from the well bore. This could be accomplished by using an adhesive that would soften upon the application of heat. This would have a disadvantage in that the adhesive would need to be removed. A preferred way to provide for disconnecting the joints would be to use an adhesive that is strong at temperatures up to 400 F. or 500 F, but that will decompose or burn at a higher practical temperature. In this way the joint could be broken with heat and would be essentially selfcleaning.

The preferred adhesive exhibiting all of the desired properties and strength is the epoxy adhesive. Epoxy adhesives can be made to thermally set in less than three minutes and to be thermally stable to a temperature of 500 F. In addition, the epoxy adhesive will decompose at elevated temperatures on the order of 1000 F. to leave an easily removable residue. A commercially available epoxy resin that will meet the requirements and exhibit the desired properties is an epoxy adhesive Number 2158 and curing agent 20863 manufactured by Minnesota Mining Company. This adhesive rapidly sets to a tensile shear strength of 5500 pounds per square inch.

When the hollow tubular sections are placed in well 11.to form well string 13, section 19 is suspended by block 37 with the lower end of the section in the well and with the upper end above the surface. Section 17 is suspended above and in alignment with section 19. The lower end of section 17 will be above the upper end of section 19. Thereafter, a nonmetallic strong adhesive is applied to at least one of the two facing ends of the suspended sections. When the adhesive is applied, the surfaces to be joined by the adhesive are cleaned of grease and water. Although some adhesives like epoxy bond Well to any surface cleaned of grease and water, the optimum surface preparation is to grit blast or roughen the surfaces with a fine grit. It is preferred that the adhesive line be of nominal thickness, for example, up to 0.01 to 0.03 inch thick. This is accomplished by spreading and pressing the surfaces together in a way that keeps the adhesive line thin.

Once the adhesive is applied to a surface, the surfaces should be placed quickly together, for example, within one minute. For maximum strength, the adhesive between the mated surfaces should be placed in compression until the adhesive sets by pressing the surfaces together. This compression is readily accomplished by lowering suspended section 17 onto the upper end of section 19 and letting section 19 support the weight of section 17 and equipment attached thereto. With the two end surfaces of sections 17 and 19 thus pressed together, the com pressed adhesive agent is heated to rapidly set the adhesive. Heating may be accomplished by any suitable means; however, curing energy is best supplied with radiant energy such as infrared energy. As mentioned previously, it is preferred that the adhesive be an epoxy and that the adhesive set within three minutes to a tensile shear strength suificient to suspend section 19 as section 17 is lowered into the well.

Section 17 is lowered with its lower end in the well and is then suspended with its upper end above the surfaces. The upper end of section 17 has a coupling with interior mating section 23. Section 25 is then suspended above and in alignment with section 17. The lower end of section 25 with exterior mating surface 27 is suspended above the receiving end of the coupling. Preferably, the adhesive is applied to this exterior surface so that when the lower end of section 25 is lowered into the coupling excess adhesive will be wiped outward away from the interior of the sections. As in the other joints, once the adhesive is applied, the lower end of section 25 is quickly lowered into the coupling compressing the adhesive between mating surfaces 23 and 27. While the adhesive is thus compressed, the adhesive is heated to quickly set the adhesive. As in the other joints, a quick-setting epoxy adhesive is preferred.

Section 25 is then lowered into the well so that joint 29 may be formed in a similar manner as joint 21 except that in joint 29 the adhesive is applied to the exterior surface on the upper end of section 25, and a coupling on the lower end of section 31 is lowered onto the upper end of section 25 so that excess adhesive is wiped downward.

Other sections are added to the string and joined in similar manners until at least fifty percent of the well string is joined with adhesive joints that sustain the tensile load on the joint.

It will be understood that various changes in the details of adhesives, the couplings and the mating surfaces which have been described herein and illustrated in order to explain the nature of this new use for adhesive joints may be made by those skilled in the art within the principle and scope of this invention, as expressed in the appended claims.

What is claimed is:

1. A method of placing hollow tubular sections in a well to form a well string comprising connecting first and second sections of hollow tubular sections composed of a material selected from the group consisting of steel or glass with an organic adhesive in a manner such that said adhesive sustains the tensile forces created by the weight of sections below said connection, lowering said adhesively connected sections into said well with said [first section being suspended by said adhesive connection from the lower end of said second section, and continuing to add sections in a similar manner until said adhesively connected sections form at least fifty percent of said well string.

2. The method of claim 1 wherein the adhesive is an epoxy base adhesive which will set within three minutes to a tensile shear strength suflicient to suspend the first section when said second section is lowered into said well.

3. The method of claim 1 wherein the step of connecting the sections includes suspending said first section of said hollow tubular sections with the lower end of said suspended first section being in said well and the upper end being above the surface, suspending said second section of said hollow tubular sections above and in alignment with said suspended first section and with the lower end of said suspended second section being above the upper end of said suspended first section, applying the adhesive to an end surface on one of said suspended sections, lowering said lower end of said second section onto said upper end of said first section thereby forcing said ends together and compressing said adhesive, and heating said compressed adhesive agent to rapidly set said adhesive.

4. The method of claim 3 wherein the adhesive is an epoxy base adhesive which will set within three minutes to a shear strength sufiicient to suspend the first section when said second section is lowered into said well,

5. The method of claim 1 wherein the step of connecting the sections includes suspending said first section of said hollow tubular sections with the lower end of said suspended first section being in said well and the upper end being above the surface, suspending said second section of said hollow tubular sections above and in alignment with said suspended first section, the lower end of said suspended second section being above the upper end of said suspended first section, said upper end of said first section having a coupling for receiving said lower end of said second section, applying the adhesive to the exterior surface of said lower end of said second section, lowering said second section into said coupling thereby forcing said ends toward each other and compressing said adhesive between the exterior surface on said lower end of said second section and the interior surface of said coupling, and heating said compressed adhesive to rapidly set said adhesive.

6. The method of claim 5 wherein the adhesive is an epoxy base adhesive which will set within three minutes to a shear strength sufficient to suspend the first section when said second section is lowered into said well.

7. The method of claim 1 wherein the step of connecting the sections includes suspending said first section of said hollow tubular sections with the lower end of said suspended first section being in said well and the upper end being above the surface, suspending said second section of said hollow tubular sections above and in alignment with said suspended first section, the lower end of said suspended second section being above the upper end of said suspended first section and having a coupling for receiving said upper end of said first section, applying the adhesive to the exterior surface of said upper end of said first section, lowering said coupling on said second section onto said upper end of said first section thereby forcing said ends toward each other and compressing said adhesive between the exterior surface on said upper end of said first section and the interior surface of said coupling, and heating said compressed adhesive to rapidly set said adhesive.

8. The method of claim 7 wherein the adhesive is an epoxy base adhesive which will set within three minutes to a shear strength sufficient to suspend the first section when said second section is lowered into said well.

References Cited UNITED STATES PATENTS 285,909 10/1883 Marsden 166242 X 1,966,248 7/1934 Kane 16649 2,498,831 2/1950 Veitch.

3,059,697 10/1962 Pitts 16649 3,101,207 8/1963 Pavel et al. 3,146,142 8/1964 Maly. 3,210,102 10/1965 Joslin. 3,231,019 1/1966 Clay et al 166-242 X 3,269,743 8/1966 Barreca.

FOREIGN PATENTS 2,497 1895 Great Britain.

CHARLES E. OCONNELL, Primary Examiner I. A. CALVERT, Assistant Examiner U .5. Cl. X.R. 166242 

